Is fasting an effective weight-loss strategy?

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Many people eat from the moment they wake up until the time they go to bed. But is this the best dietary pattern for our health?

Fasting as a dietary practice for weight loss has gained considerable popularity over the years. By now you’re probably familiar with, or have at least heard of, the 5:2 diet or the 800-calorie diet. But now there’s a new kid on the block that’s looking quite promising for weight loss and might just be an easier fasting regimen to implement into your lifestyle—“time restricted feeding” aka the 16:8 diet.

What is fasting?

Calorie-Restricted Fasting: fasting via restriction of calories. The 800 calorie diet, made famous by Michael Mosley, promotes reduced calories to achieve weight loss and a reduction in blood sugar.

Intermittent Fasting: a fast involving calorie restriction on a select few days of the week. This involves a fast (or calorie restriction) on 1-4 days per week, more commonly recognised as the 5:2 diet.

Time-Restricted Feeding: a new variation on intermittent fasting, whereby the restriction is applied to the time spent eating, rather than the focus be on restricting calories. Generally, feeding hours occur within an 8-hour period. Some now refer to this as the 16:8 diet.

Why does it work?

Being overweight, or obese, increases the risk of many metabolic diseases, such as heart disease and type 2 diabetes. And there’s growing evidence suggesting that even small amounts of weight loss can lead to improvements in metabolic health. Fasting is proposed to achieve weight loss through giving your metabolism a jolt.

Human trials published in reputable journals, such as Obesity, American Journal of Clinical Nutrition and Metabolism, have demonstrated weight loss of 3-8% over 8 to 52 weeks of treatment with intermittent fasting. This was accompanied by drops in blood pressure, cholesterol, triglycerides and insulin resistance!

Research is also mounting about the benefits of time-restricted fasting. In fact, a 2016 and a 2017 study revealed a significant decrease in body fat without any loss in lean muscle in young, resistance-trained males. The time restricted feeding appears to assist in body fat loss through metabolic influence and a reduction in daily calorie intake (without counting calories).

A pilot study published in 2018 also found benefits in systolic blood pressure. Research participants applied an 8-hour time restricted feeding intervention. They had an “eating window” of 10am to 6pm and were allowed water, black tea or black coffee only outside of these hours. In just 12 weeks, they were reaping the benefits!

How to do it

Time-restricted feeding is very easy to do—simply choose the hours in which you will eat your food (calories) during the day, making sure it’s a period of 8 hours.

For example, if you normally eat your first meal at 8 am and keep eating until around 9 pm, then you are eating all your food in a 13-hour window each day. To use time-restricted feeding, you would reduce this number to an 8-hour window, for example 10 am to 6 pm. This essentially removes one or two of the meals or snacks you usually eat.

Is it safe?

Time-restricted feeding is a safe practice that poses no adverse events. However, these dietary strategies do not suit everyone as everyone’s lifestyle is different! Whether you’re juggling multiple kids at home or working shift work, if you find fasting techniques a struggle, it’s always a good idea to seek support and guidance from a dietitian.


Although recent research shows that intermittent fasting (5:2 diet) is effective for weight loss, it can be hard to stick to long-term. Time Restricted Fasting or the 16:8 diet seems to be more user friendly and appears to provide the same health benefits without having to restrict calories and feel hungry.

Why not give it a go? Speak to one of our dietitians for more guidance on the 16:8!

Sue Radd is an Advanced Accredited Practising Dietitian and one of Australia’s leading nutritionists and health communicators. Her most recent book Food as Medicine: Eating for Your Best Health received the Gourmand World Cookbook Award for Best Health and Nutrition Book in the world for 2016.

Category: Attitude, Lifestyle, Physical Health

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